Billy Apple Posted November 19, 2012 Share Posted November 19, 2012 I'm selling a Matamp 212 cab in the Market Place. The cab is 4 ohm and rated at 400w. I've had a PM from a guy with a Markbass LM3, which is rated at 500w at 4 ohm. He seemed to think that the head would break the cab. I know this not to be true, but I don't know the science to explain why. Can anyone help? Thanks! Quote Link to comment Share on other sites More sharing options...
LawrenceH Posted November 19, 2012 Share Posted November 19, 2012 (edited) Because the 400 watt rating is based on the speakers' continuous average thermal power handling. Under normal circumstances a 500 watt amp couldn't put out 400 watts average power using a bass guitar (or any musical) signal, so unless you use test tones rather than play music you won't be able to destroy those speakers by overheating. In the interests of a complete answer, too much very low bass WOULD let you damage them with less than 500 watts, but this is true of nearly every cab even some with much higher thermal power handling, and it's really not something to worry about with your Matamp. Edited November 19, 2012 by LawrenceH Quote Link to comment Share on other sites More sharing options...
Billy Apple Posted November 19, 2012 Author Share Posted November 19, 2012 Cheers Lawrence Quote Link to comment Share on other sites More sharing options...
Mr. Foxen Posted November 19, 2012 Share Posted November 19, 2012 Watts don't break cabs. Stupid breaks cabs. Ask him if he's stupid, if he says 'no', you can assure him in that case the cab won't break. That's science. Quote Link to comment Share on other sites More sharing options...
davekent Posted November 19, 2012 Share Posted November 19, 2012 Thanks for your response to the above question. In answer to the post above this, no I'm not stupid. I just didn't understand the science behind watts rating. Quote Link to comment Share on other sites More sharing options...
mcnach Posted November 20, 2012 Share Posted November 20, 2012 [quote name='Mr. Foxen' timestamp='1353351721' post='1874141'] Watts don't break cabs. Stupid breaks cabs. [/quote] Quote Link to comment Share on other sites More sharing options...
Lozz196 Posted November 21, 2012 Share Posted November 21, 2012 Yep, your ears should let you know when a cab is being pushed too far. Besides, I can`t imagine needing to run a 500 watt amp at full blast, so doubt it would get to the point where this would happen. Quote Link to comment Share on other sites More sharing options...
Phil Starr Posted November 22, 2012 Share Posted November 22, 2012 Your amp's rating is the maximum power it will give without distorting. Try turning it up high and play a really loud note and listen. If you can watch the speaker cone. The first snap on the string will make the cone jump forwards and the sound will be really loud. This dies away quite quickly but the sound continues quieter and quieter for a long time depending upon your actual bass. The amp and speaker are only dealing with full power for a few thousandths of a second, the first hit of the pick or your finger. The average power to the speakers is a lot less than the maximum power the amp can produce. Two things will break your speaker. Depending upon the design of the actual speaker units the first impact sounds may push the speaker cone too far and it will hammer against the back of the magnet making a loud 'farting' sound or worse still it will go out of the front of the magnet. Good speakers will be designed to prevent this but you can break speakers this way. This isn't in the speakers power rating because it depends upon the detailed design of the cab it is in. The second way is caused by all the electrical power from your amp heating up the tiny coil of thin wire at the heart of your speaker. The wattage rating of your speaker is actually the amount of heat it can dissipate before it gets hot enough to start damaging things. Speaker components can get as hot as an old fashioned light bulb. Because the important thing is the average power and your sound rapidly decays as you have heard and because of the gaps in the music you can generally reckon a 500W amp flat out but without distortion is probably averaging less than 50W. Usually it will be even lower than this. A 500W amp averaging 50W isn't going to blow a 100W speaker by overheating never mind a 400W speaker unless you are doing something else unusual. It might 'pop' the 100W speaker but it isn't going to threaten the 400W speaker in all probability. In any case using this system turned up full will drown out the drums and damage the hearing of anyone standing too close. So long as you don't turn up loud enough to make 'farting' noises or any other unusual sounds and you don't use stupid amounts of distortion/compression or bass boost this combination should go on working for years. Quote Link to comment Share on other sites More sharing options...
mentalextra Posted November 24, 2012 Share Posted November 24, 2012 Watts dont break cabs, distorted watts does! Quote Link to comment Share on other sites More sharing options...
3below Posted November 24, 2012 Share Posted November 24, 2012 (edited) [quote name='Mr. Foxen' timestamp='1353351721' post='1874141'] Watts don't break cabs. Stupid breaks cabs. Ask him if he's stupid, if he says 'no', you can assure him in that case the cab won't break. That's science. [/quote] agree, and put another way, when it sounds like you are destroying your speakers, you are. When it 'farts' turn it down. Action: Point to volume control in exaggerated way. I find the Crown XTi 6000 has plenty of 'headroom' into the 4" speaker 2.5W bass cab. Just unable to get the volume knob above 0.5 Have not destroyed the speaker yet. Edited November 24, 2012 by 3below Quote Link to comment Share on other sites More sharing options...
LawrenceH Posted November 25, 2012 Share Posted November 25, 2012 [quote name='3below' timestamp='1353791567' post='1878578'] agree, and put another way, when it sounds like you are destroying your speakers, you are. [/quote] Except if you're using fuzzy distortion. Fairer to say inexperience, rather than stupidity. More generally, a factor that people preaching about excursion versus thermal limits ignore, is that the magnet is itself a major thermal design element. Push the voicecoil out of the gap and you rapidly reduce thermal capabilities unless the design allows for this. The thermal rating tests are bandwidth-limited, but a 'modern' xmax definition can allow the voicecoil to leave the gap by as much as 1/3rd total gap height, greatly reducing the thermal capability. Factor in a player's (perhaps subconscious) compensation for gradually increasing speaker power compression and you can potentially hit a new, compromised thermal limit [i]before you hit xmax, ie no easily audible warning.[/i] Add to this that newer generation premium drivers can show a less rapid transition from clean to gak [i]above[/i] xmax, all the while reducing thermal capability further and further, and it can be very difficult to judge where the limits are unless you are pretty experienced at blowing that particular speaker model! I have heard rubbing voicecoils that are probably damaged by overexcursion, but the few times I've looked at the voicecoil of a fully 'blown' speaker I've seen signs of heat damage. Quote Link to comment Share on other sites More sharing options...
Mr. Foxen Posted November 25, 2012 Share Posted November 25, 2012 Power compression is one of the the 'my rig was getting quieter so I turned it up some more, then there was a smell, so I turned it up more' thing that you hear often as a tech. Quote Link to comment Share on other sites More sharing options...
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